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We present the facile technique of colorimetric SNP analysis through DNA-templated cooperative complexation between a luminescent lanthanide ion (Ln(3+): Tb(3+) or Eu(3+)) and two ODN (oligodeoxyribonucleotide) conjugates carrying a metal chelator. Ethylenediaminetetraacetic acid (EDTA) and 1,10-phenanthrorine (phen) were covalently attached to ODNs to form the conjugate probes, capture and sensitizer probes, respectively. The sequences of the conjugates were designed so as to form a tandem duplex with a target with their auxiliary units facing each other, providing a microenvironment to accommodate Ln(3+). The capture probes for the wild-type (wt) and the mutant (mut) of thiopurine S-methyltransferase gene, were mixed with equimolar amounts of Tb(3+) and Eu(3+), respectively. Then both of the allele specific capture probe solutions and the sensitizer probe were added to three different solutions containing the targets, wt/wt (G/G), mut/mut (C/C), and wt/mut (G/C). The solutions emitted in green, red, and yellow, respectively; the colors were identified even by the naked eye.

A versatile molecular device (lanthanide-complex molecular beacon; LCMB) was prepared by tethering ethylenediaminetetraacetic acid to the 5'-end and 1,10-phenanthroline to the 3'-end of stem-loop structured DNA as metal-capturing and sensitizer moieties, respectively. The emission from LCMB responded to the target molecule through the reversible structural change.

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